1. Field of the Invention
The invention relates to a drive unit and a vehicle equipped therewith.
2. Description of the Related Art
Heretofore, there has been proposed a drive unit of this type wherein a fuel cell, a secondary battery, a large-capacitance capacitor, and an electrolyzer are connected in parallel to a drive circuit for driving a motor without the intervention of a voltage converter and wherein a first switch for cutting the fuel cell and the secondary battery off from the drive circuit and a second switch for cutting the electrolyzer off are provided (Japanese Patent Application Laid-Open No. 6-253409 (FIGS. 1 and 2, page 4)). The first and second switches are on and off respectively during normal operation of this unit. When regenerative control of the motor is performed, the first switch is turned off to cut the fuel cell and the secondary battery off from the drive circuit, so that the large-capacitance capacitor is charged using regenerative power. If an inter-terminal voltage of the large-capacitance capacitor rises above an inter-terminal voltage of the secondary battery, the second switch is turned on, so that the electrolyzer electrolyzes water using regenerative power and electric power obtained from the large-capacitance capacitor. Hydrogen and oxygen obtained by electrolyzing water are used as fuel for the fuel cell.
In the drive unit thus constructed, however, every time regenerative control of the motor is performed, the first switch needs to be turned off to cut the fuel cell and the secondary battery off from the drive circuit. In the case where regenerative control of the motor is frequently performed, the more complicated the control becomes, the more the load applied to the first switch increases.
This drive unit is provided with the secondary battery and the electrolyzer. Therefore, if the drive unit becomes complicated, both the secondary battery and the electrolyzer become complicated. For size reduction or simplification of the unit, the unit may dispense with the secondary battery and the electrolyzer. In this case, however, when the fuel cell is connected again after having been cut off by the first switch, a large current may flow between the fuel cell and the large-capacitance capacitor if the inter-terminal voltage of the large-capacitance capacitor assumes a certain value. Such a large current causes an inconvenience such as reduction of a life span of the switch.